THE DEPOSITJON OF COPPER 43 I 



A number of attempts has been made to discover the condi- 

 tions under which copper may be deposited by solutions of ferrous 

 salts. As earl}' as 1861, Knop succeeded in forming cuprous 

 hydroxide by treating a mixture of cupric and ferrous sulphates 

 with alkaline carbonate.' In one instance he speaks of obtaining 

 traces of copper. In i864,Wibel repeated Knop's experiments,^ 

 but was unable to verify the latter's statement regarding the 

 reduction to metallic copper. When, however, a mixture of fer- 

 rous and cupric hydroxides, formed by adding potassium 

 hydroxide to a solution of the sulphates, was heated to 210^ C, 

 traces of copper were obtained. Solutions of the sulphates and 

 coarsely powdered Wollastonite, subjected to the same treat- 

 ment, yielded a like result. The separation of metal, however, 

 was slight and the part played by the ferrous hydroxide in the 

 reduction was at the time somewhat questioned. In 1867, Braun 

 observed the partial deposition of copper from a mixture of 

 ferrous and cupric salts when these were dissolved in large excess 

 of ammonium carbonate. ^ The same year Weith secured a ready 

 reduction in the presence of tartaric acid.-* He failed to note, how- 

 ever, that under the same conditions, the organic acid itself will 

 slowly reduce the copper salt. A mixture of calcium hydroxide 

 with a solution of ferrous and cupric sulphates, was allowed to stand 

 for several weeks. The precipitate thus obtained, when treated 

 with acetic acid, left a residue of cuprous oxide and copper. 



Strangely enough Weith overlooked the fact that cuprous 

 oxide with acetic acid yields cupric acetate and metallic copper. 

 In i86g, Hunt^ stated that he had obtained metallic copper by the 

 action of cupric chloride on freshly precipitated ferrous hydroxide, 

 or carbonate. Nothing is given, however, to indicate that the 

 metal was actually detected by isolating it from co-precipitated 

 ferric hydroxide. 



'A. Knop: N. Jahrb. f. Min. (1861), S. 513. 



*Ferd. Wibel: "Das Gediegen-Kupfer und das Rothkupfererz " (1S64), S. 14. 



3E. Braun : Zeit. fiir Chem. (1867), 569. 



■t W. Weith : Zeit. fur Chem. (1867), 623. 



sSterry Hunt: Comp. r. (1869), 1357. 



